An x-ray system for producing a specimen image in color



Jan. 11, 1966 sABURo sAsAo 3,229,089

STEM FOR PRODUCING A SPECIMEN IMAGE IN COLOR AN X-RAY SY 2 Sheets-Sheet 1 Filed OCT. 25

Jan. 11, 1966 sABURo ssAsAo 3,229,089

AN X-RAY SYSTEM FOR PRODUCING A SPECIMEN IMAGE IN COLOR Filed Oct. 25, 1962 2 Sheets-Sheet 2 KoQ 0 l l 0.3 5.4 0.5 0.6 0.7 0.8 afS 0./0 0J/ ya j /0 INVENTOR.

SAEZ/A20 .SO-75nd P URC i A C OWER $0 E 7 United States Patent O 3,229,089 AN X-RAY SYSTEM FR PRODUCING A SPECIMEN IMAGE IN COLOR Saburo Sasao, Higashisumiyoshi-ku, Osaka, Japan, assignor to Hayalrawa Denki Kogyo Kabushilri Kasha, Osaka,

Japan, a company of Japan Filed Oct. 25, 1962, Ser. No. 233,096 4 Claims. (Cl. Z50-65) This invention relates to X-ray systems and specifically to a novel and improved method and apparatus particularly useful for X-ray materials that may be heterogenous in structure, including substances having diflferent masses or be of irregular configuration.

It is well-known that X-rays of different wavelengths have different penetrating power and that the shorter wavelengths or harder X-rays have greater penetrating power than the longer wavelengths or soft X-rays. The penetration of a given X-ray through a material varies generally in the proportion of the cube orf the mass so that if a hard X-ray is used for the purpose of obtaining an X-ray picture of a low density material, there will be little absorption -of the X-ray, and the interior structure of the specimen will not be discernible in the resultant visible image. If so-ft X-rays are used with a material of high density, it is obvious that an X-ray image will not be produced, since all of the X-ray energy will be absorbed by the specimen. Should the specimen being X-ray have both low and high densities, the use of 4a soft X-ray would, of course, produce an image of the high density material. It has therefore been essential that the X-ray wavelength be carefully selected to produce a useful image of the interior of a specimen or body being X-rayed.

This invention overcomes -the difficulties heretofore encountered in X-raying materials and particularly com- |posite materials `and provides a new and improved systern for X-raying specimens to .provide a high degree of detail in the resultant image, notwithstanding the composition of the body or specimen being X-rayed.

Another object of the invention resides in the provision of a novel and improved X-ray system for producing images of the interior of a body being X-rayed that is characterized by its versatility, dependability and ease of operation and maintenance.

Still another object of the invention resides in the provision of a novel and improved system for X-r-aying bodies wherein the resultant image is displayed in color to provide an indication of the relative densities of the different materials forming the body.

Still another object of the invention resides in the provision of a novel and improved X-ray system for displaying X-ray images in color wherein the colors of the various .portions of the image identify materials of different masses and wherein the thickness of a particular :portion of the specimen or body can be determined by the brightness of the image.

Still another object of the invention resides in the provision of a novel and improved method and apparatus for X-raying objects.

The above and other objects and advantages of the invention will become more apparent from the following description and accompanying drawings forming art of this application.

In the drawings:

FIGURE 1 is a block diagram showing an X-ray system in accordance with the invention.

FIGURE 2 is a graph illustrating the mode of producing extremely narrow bands of X-rays of selected wavelengths.

FIGURE 3 is a graph showing one mode of control of the image-reproducing apparatus to produce an image "ice wherein the brightness provides an indication of the thickness of portions of the body being X-rayed.

FIGURE 4 is la modification of the embodiment of the invention shown in FIGURE 1.

The X-ray system in yaccordance with the invention utilizes means for generating relatively narrow bands of X-rays of different wavelengths with the bands of X-rays being sequentially directed through a body being X-rayed. The X-ray image is converted into visible light by the utilization of a suitable fluorescent .plane with the result that a detailed image of the internal structure of the body is produced. The invention further contemplates the cooperation of a novel and improved X-ray system with reproducing means for reproducing the image on the fluorescent plate in color wherein the different colors represnts different densities of portions of the body being X-rayed. Through an improved control of the brightness of the image, an indication of the thickness of selected portions of the image can also be obtained.

Referring now to the drawings land more specifically to FIG. 1, the numeral 1 denotes an X-ray tube having a cathode 22 and an lanode 23. The anode 23 is formed of three segments or targets 23a, 23b and 23e. For the purpose of this description, let it he assumed that the target 23a is formed of molybdenum, the portion 23h of copper, and the portion 23C of cobalt. The cathode is preferably formed so that electrons emitted by the cathode will impinge on the anode and be reflected outwardly in a direction generally denoted by the broken line. During operation of the device, the anode is rotated at high speed by means of a synchronous motor 24 energized by an alternating current power source 10. High voltage is applied between the cathode and anode by means of a suitable high voltage generator 21 connected at one side to the cathode and at the other side to the power source 10.

The X-rays generated by the tube 1 `are projected outwardly therefrom and pass through a filter disc `2. This disc is provided with three segmental portions 2a, 2b and 2c. The disc is driven by a synchronous motor 13 which is fed from the power source 16 so that it will rotate at exactly the same speed as the anode 23 of the X-ray tube 1. By way of example, the segmental portions 2a, 2b and 2c of the filter disc 2 may be formed respectively of zirconium, nickel and iron. The frequency of the :power source 10 is controlled by a frequency generator 11 which fixes the frequency of the power source 10 and thereby the rate of rotation of the anode 23 and the filter disc 2. At the same time, a signal from the frequency generator 11 is fed to the high voltage supply 21 and causes the high voltage supply to produce high voltage pulses of selected magnitudes. In the present illustration, when the electron beam is being projected onto the segmental portion 23a of the anode, the high voltage generator 21 applies 20 kilovolts to the cathode. When the electron beam is directed on segment 231;, the generator applies nine kilovolts to the cathode, and when the beam is directed on anode segment 23C, the high voltage generator produces approximately eight kilovolts.

Inasmuch as the anode 23, the filter disc 2 and the high voltage supply 21 are synchronized in their operation, twenty kilovolts will be applied to the cathode 22 during the period that the segment 23a of the anode passes beneath the cathode. At the same time, the segment 2a of the filter disc 2 intercepts the beam thus produced. This action will produce an exceedingly narrow band of X-rays which for practical purposes may beconsidered to be a single frequency X-ray. The procedure for the attainment of this narrow band is illustrated in FIG. 2 in which the abscissa represents the wavelength of the X-ray in angstroms, and the ordinate represents the strength of the X-ray beam produced. The two peak intensities are socalled spectral lines which are lcharacteristic of molybdenum of which the anode segment 23a is formed. The shorter Wavelength peak is denoted by K, while the longer wavelength peak is denoted by Ka. While the total amplitude of the two peaks is not shown in the graph, the amplitude of Kot is very much larger than K13. The band of X-rays as illustrated in FIG. 2 then passes through the filter segment 2a which is formed of zirconium. In so doing, the zirconium is substantially transparent to the frequency Kot and largely attenuates the frequency K with the result that the X-ray energy directed on the body 3 being X-rayed will be of an extremely narrow band of wavelengths having an average Wavelength of approximately .71 angstroms.

When the anode 23 and filter 2 have rotated to bring the target 23b into operation and the filter segment 2b in line with the projected X-ray beam, a characteristic line spectrum will be produced by the copper segment of the anode and subsequent filtering by the nickel segment 2b will produce a narrow band of X-rays having an average frequency of approximately 1.54 angstroms. When the anode segment 23e which is formed of cobalt is bombarded with a cathode beam at a potential of eight kilovolts and the resultant X-ray is filtered by iron segment 2c of the filter 2, a relatively narrow band of X-rays having an average wavelength of 1.79 angstroms is produced. Thus, the X-ray beam directed onto the body being X-rayed will be formed of X-rays of three different hardnesses generated sequentially and at a relatively high repetition rate.

It is to be understood, however, that while specific materials and voltages have been utilized in describing the foregoing example, it is evident that other target and filter materials and anode voltages may be employed to effect the desired ends. Furthermore, it is possible to utilize any number of selected X-ray bands depending on the precision that may be required. For instance, in cases Where the body being X-rayed may embody materials of just two different masses, an X-ray beam of two different hardnesses may be employed. On the other hand, where a more complicated body or object is being X-rayed, it may be desirable to utilize four or more different X-ray bands. Furthermore, it is also possible in accordance with the invention to vary other elements of the X-ray generating apparatus. For instance, if a grid controlled X-ray tube is employed, the grid voltage may be varied in synchronism with the other elements described, and in certain instances, it may be desirable to vary the cathode heating current.

The invention further contemplates an improved viewing system for utilization with the X-ray generating and filtering apparatus thus far described. As pointed out above, the X-ray beams of different hardnesses are directed onto an object 3 to be X-rayed, and an image is formed on a suitable fluorescent screen 4. The fluorescent screen may be of any suitable material, as, for instance, zinc sulfide, so that a visible image of the X-ray beam is produced thereon. This image is scanned by an electron camera 5, such as a videcon or other similar device for conversion of visual images into electrical signals. The electrical signals from the camera 5 are fed to a switching circuit 6 that provides three separate sequential signals representing red, green and blue, the primary colors customarily used in the transmission of images in color. The switching operation of the switching circuit 6 is controlled by the frequency generator 11 so that its operation is coordinated with the rotation of the X-ray tube anode 23 and the filter 2 as previously described.

By way of example, the image which appears on the fluorescent screen 4 as a result of the hard X-rays having a wavelength of the order of .71 angstroms has been selected to produce a red signal from the switching circuit 6. The second X-ray beam having a wavelength of 1.54 angstroms will produce a green signal, while the softest X-ray beam having a wavelengthV of 1.79 angstroms will produce the blue signal. The three signals now leaving the switching circuit 6 are fed to an image amplifier 7, and the output of the amplifier 7 is then fed to an imagereproducing tube S which may have any suitable contiguration for the production of colored images. Conventional picture tubes presently available are most satisfactory for this purpose. In order to coordinate and synchronize the scanning of the camera 5 with the picture tube 3, scanning signals are produced by a generator 12 and fed both to the camera 5 as Well as to the magnetic scanning coil 8 on the tube 8. It is evident, however, that electrostatic scanning may be used in place of the magnetic deflection yoke 8.

With the foregoing arrangement, the individual pictures produced on the iluorescent screen 4 are presented on the screen of the picture tube `8 in three separate colors or combinations thereof so that the colored rendition of the resultant image will provide a detailed picture of the internal structure of the specimen 3, and the colors will constitute an indication of the densities of the various portions of the specimen 3. Inasmuch as the switching speed is relatively high so that the eye cannot distinguish the three separate images One from the others, -a composite picture is produced and thereby greatly facilitates a more accurate analysis of the specimen. For instance, let it be assumed that I is the intensity of an X-ray beam which permeates a specimen being investigated; that I0 is the intensity of the X-ray impinging on the specimen; X is the thickness of the specimen; and ,u is the attenuating rate of the specimen, the attenuating rate being a function of the hardness of the X-ray and the absorbing rate of the specimen and generally proportional to the cube of the density of the specimen. The intensity of the X-ray leaving the specimen 3 can then be determined by the following equation:

IZIOCFMX Thus, it will be seen that even when a specimen being investigated is formed of a single material, the permeation of the specimen by the X-rays will vary in accordance with the thickness of the object, and in accordance with the present invention, the color of the resultant image will vary in accordance with thickness. While in many cases the variation of color in accordance with both the mass of part of the specimen and with variations in thickness of the specimen will not be objectionable, it has been found desirable to modify the characteristics of the amplifier 7 to obtain a modified amplifying function to facilitate proper interpretation of the image. l

The modification of the amplifier 7 is illustrated in FIG. 3; When the thickness of the specimen or a portion of the specimen varies, the permeation of the X- rays does not vary linearly and therefore the color of the image will vary according to the thickness of the specimen. To minimize this variation, the amplifier 7 is Y given a nonlinear characteristic so that the brightness of an image formed by -a given X-ray beam will have a linear characteristic with reference to thickness. FIG. 3 shows the variation of the intensity of the X-ray beam leaving a specimen versus the thickness of the specimens, and the curves are denoted by the letters R, G and Bf By imparting a nonlinear characteristic to the amplifier 7, the brightness `of the image on the screen of the tube S will vary substantially linearly with changes in thickness of the specimen or portion thereof. The resultant va-riation of brightness is represented by the broken lines R', G and B since the variations in thickness X will produce a linear change in the brightness of the image on the screen of tube 8.

A modified form of the Y -ray producing apparatus in accordance with the invention is shown in FIG. 4. In this case, a normal X-ray tube 31 is provided, having a cath- X-ray beam P which is directed onto the inner surface of a cylindrical ring 32. The ring 32 is formed of three separate crystals 32a, B2b and 32C, and the ring may be supported in any suitable manne-r to facilitate rotation at a relatively high speed. The ring may be driven by a suitable apparatus, as, for instance, synchronous motor 33 driving a rubber disc 34, the latter being resiliently urged against the cylindrical ring 32 in order to effect rotation thereof. The motor 33 is fed from the synchronized signal from the generator 110` as shown and described in connection with FIG. 1 so that the rotation of the ring will 'be synchronized with the lter 2 as shown in FIG. 1.

With the foregoing structure and with the crystals 32a, 32h and 32C being of diiferent materials, the wavelength of the X-radiation reflected from the crystal will be characteristic of the crystal and accordingly, exceedingly narrow bands of radiation P may then be directed through a filter 2 or directly onto the specimen or body 3 being X-rayed. In actual practice, it would be desirable to form the rotating element of FIG. 4 of a suitable supporting material and line the inner surface thereof with appropriate crystals. I-nasmuch as the particular wavelength of radiation reflected from a crystal is fundamentally a characteristic of the crystalline structure, it would be possible to use one type of material on the inner surface of the ring with the several sections arranged with different crystalline structures. It is also possible to use material of the same crystalline structure but with the structures of the three sections having diiferent crystal orientations.

While only certain embodiments of the invention have been illustrated and described, it is apparent that alterations, modifications and changes may be made without departing from the true scope and spirit thereof as defined by the appended claims.

What is claimed is:

1. An X-ray system comprising means generating coincident X-ray beams of two different wavelengths, said beams being generated alternately and repetitively, a specimen adapted to be irradiated by said X-ray beams, means for converting said X-rays permeating said specimen into a light image, a photoelectric scanning camera tube converting said repetitive images into electric image signals, an image reproducing tube for reproducing electric image signals in color, at least two amplifiers, switching means connecting said camera tube to said amplifiers alternately .and repetitively, connections between said ampliiers and said image reproducing tube to form coincident images in diiferent colors, and means synchronizing said X-ray generating tube with said switching means and said image reproducing tube whereby an X-ray beam of one wavelength will produce an image of one color and an X-ray beam of another wavelength lwill produce an image of another color, each color image being representative of the absorption coeficient, density and thickness variations in the specimen, said colored images being produced at a rate which results in a single multicolored image when received by the eye.

2. An X-ray system according to claim 1 whe-rein said X-ray generating means produces repetitive beams of at least three different wavelengths and said `system includes at least three amplifiers and a three color image reproducing tube `for producing three repetitive coincident images in different colors.

3. An X-ray system according to claim 1 wherein said X-ray generating means comprises an X-ray tube having at least two anodes, a cathode for generating an electron ybeam and means for moving said anodes relative 'to said beam.

4. An X-ray system according to claim 1 including means for modifying the amplifying characteristic of each amplifier to compensate for X-ray absorption of the specimen as a result of the thickness of said specimen.

References Cited by the Examiner UNITED STATES PATENTS Re. 25,118 1/1962 Graves Z50-65 2,963,585 12/1960 Ecek Z50-83.3 2,999,935 9/1961 Foster Z50-83.3 2,999,937 9/1961 Kohler Z50-86 3,004,101 10/1961 Jacobs et al. Z50-65 3,004,163 10/1961 Edholm Z50-83.3 3,114,832 12/1963 Alvarez 250-86 RALPH G. N'ILSON, Primary Examiner. 

1. AN X-RAY SYSTEM COMPRISING MEANS GENERATING COINCIDENT X-RAY BEAMS OF TWO DIFFERENT WAVELENGTHS, SAID BEAMS BEING GENERATED ALTERNATELY AND REPETITIVELY, A SPECIMEN ADAPTED TO BE IRRADIATED BY SAID X-RAY BEAMS, MEANS FOR CONVERTING SAID X-RAYS PERMEATING SAID SPECIMEN INTO A LIGHT IMAGE, A PHOTOELECTRIC SCANNING CAMERA TUBE CONVERTING SAID REPETITIVE IMAGES INTO ELECTRIC IMAGE SIGNALS, AN IMAGE REPRODUCING TUBE FOR REPRODUCING ELECTRIC IMAGE SIGNALS IN COLOR, AT LEAST TWO AMPLIFIERS, SWITCHING MEANS CONNECTING SAID CAMERA TUBE TO SAID AMPLIFIERS ALTERNATELY AND REPETITIVELY, CONNECTIONS BETWEEN SAID AMPLIFIERS AND SAID IMAGE REPRODUCING TUBE TO FORM COINCIDENT IMAGES IN DIFFERENT COLORS, AND MEANS SYNCHRONIZING SAID X-RAY GENERATING TUBE WITH SAID SWITCHING MEANS AND SAID IMAGE REPRODUCING TUBE WHEREB AN X-RAY BEAM OF ONE WAVELENGTH WILL PRODUCE AN IMAGE OF ONE COLOR AND AN X-RAY BEAM OF ANOTHER WAVELENGTH WILL PRODUCE AN IMAGE OF ANOTHER COLOR, EACH COLOR IMAGE BEING REPRESENTATIVE OF THE ABSORPTION COEFFICIENT, DENSITY AND THICKNESS VARIATIONS IN THE SPECIMEN, SAID COLORED IMAGES BEING PRODUCED AT A RATE WHICH RESULTS IN A SINGLE MULTICOLORED IMAGE WHEN RECEIVED BY THE EYE. 